Air conditioning unit having high and low capacity operation



L. W. AIR CONDITIONING UNIT HAVING HIGH ATCHISON June 26, 1962 AND LOW CAPACITY OPERATION Filed Dec. 29, 1960 INVENTOR. LEONARD W ATCHlSON BY ZZ/W H\5 ATTORNEY United States Patent 3,040,544 AIR CONDITIONING UNIT HAVFNG HIGH AND LOW CAPACETY GPERATIGN Leonard W. Atchison, Louisviile, Kym, assignor to General Electric Company, a corporation of New York Filed Dec. 29,1960, Ser. No. 79,368

3 Claims. (Cl. 62267) The present invention relates to a room air conditioning unit more particularly to an improved arrangement in 'such a unit for modifying the capacity of the unit accord vide an arrangement whereby at least the indor fan may be operated atreduced speed according to the desires of the operator. The reduced fan speed does lower the capacity of the unit to some extent but is considered desirable from a noise reduction standpoint at certain'times, such as at night, when the heatingor cooling load of the room is usually at a minimum. 1 t

The components of an air conditioner are usually designed to operate at maximum efliciency for only one set of parameters. Thus, the heat exchangers of an air conditioner are designed to condense and evaporate the refrigerant flowing through the system at a particular rate for a certain quantity of air flowing at certain temperatures over the heat exchanger. The quantity of air flow for which the heat exchangers are specifically designed is that which is provided by thefans when operated at maximum speed. Thus a reduction in speed of either of the fans, or both of the fans, "usually has a substantial effect on the refrigerant flow through the system and is likely to result in conditions unsatisfactory to most ellicient operation of the unit. One such condition, which has occurred in units of the type when used for cooling a room with the indoor fan operating at reduced speed,

is a very substantial reduction in the operating temperature of the indoor heat exchanger which results in a frost,

or ice build up. This condition is likely to occur during the night when the outdoor temperature falls and there is a heat load in the room which, for one reason or another, cannot be satisfied by the quantity of air being cooled by the indoor heat exchanger. Frost build-up on the indoor heat exchanger, of course, further impairs the air flow through this heat exchanger and hasthe effect of further aggravating this situation. Thefrost build-up may also create an extraordinary amount of water. in the unit whenthe unit is deenergized and the ice on'the indoor heat exchanger melts. This condition sometimes results in water overflowing into the enclosure which, of course, is likely to cause extensive damage. It has been found desirable, therefore, to reduce the capacity of the refrigeration system, or to modify the amount of refrigerant flowing through the refrigeration system, to an amountwhich can be safelyhandled by the indoor heat exchanger in -accordance with the quantity of air flowing thereover,

Accordingly, itis an objectof the present invention a to provide an improved arrangement for simultaneously reducing the capacity of the refrigeration system whenever the fan motor is conditioned to operate atlow speed.

A more specificobject of the present invention is to provide an airlconditiening unit having an improved 3,040,544 Patented June 26, 1962 2 refrigeration system incorporating means for throttling flow of refrigerant through the suction line from the evaporator to the compressor whenever the evaporator fan is conditioned to operate at reduced speed.

Further objects and advantages of the invention will become apparent as the following description proceeds, and the features of novelty which characterize the invention will be pointed outwith particularity in the claims annexed to and forming a part of this specification.

In carrying out the objects of the present invention there is provided an air conditioning unit including a case adapted for mounting in an outer wall of a room and including openings'communicatin-g with indoor and outdoor air respectively. Mounted within the case is a refrigeration system including a compressor, an outdoor heat exchanger and an indoor heat exchanger suitably connected in refrigerant flow relationship. An outdoor fan is provided for circulating a stream of outdoor air over the outdoor heat exchanger and, similarly, an indoor fan is provided for circulating indoor air over the indoor heat exchanger. Means are provided for selectively 'conditioning, at least, the indoor fan to operate at a reduced speed thereby reducing the noise output of this fan. In order to reduce the refrigeration capacity of the system in accordance with the reduced flow of air over the indoor heat exchanger, a throttling means is provided in the suction line between the heat exchanger and the compressor which is energized simultaneously with the conditioning of the indoor fan to low speed operation thereby restricting the flow of refrigerant from the indoor heat exchanger to the compressor and, thus, reducing the rate of refrigerant flow through the system.

For a better understanding of the invention reference may be had to the accompanying drawing, in which:

FIG. 1 is a somewhat diagrammatical cross-sectional view of an air conditioner to which the present invention is applicable; and

FIG. 2 is a line diagram illustrating in schematic form the refrigeration system and fans of an air conditioning unit and an electrical circuit arrangement for changing the speed of the fan motor and for modifying the refrigerant flow rate of the system in accordance with the change in fan motor speed.

Referring now to PEG. 1, there is shown an air conditioning unit comprising a metallic case 2 which is divided by a barrier 3 into two separate compartments designated the condenser or outer compartment 4 and the evaporator or inner compartment 6. A condenser 7 is positioned across the lower end of the condenser compartment 4 and ,an evaporator 8 is disposed across the opposite. end of the evaporator compartment 6. The evaporator 8 and condenser 7 are connected in refrigerant flow relationship with a compressor 9 which is also located in the outer or condenser compartment 4. More specifically, as may be seen in FIG. 2, a suction tube 5 delivers low pressure suction gas to the compressor and a discharge tube 10 is connected to the compressor 9 for delivering high pressure, high temperature discharge gas to the condenser 7. Suitable means, such as a capillary tube 15 is connected between the condenser and the evaporator for creating a pressure drop between the condenser 7 and the evaporator 8 to promote vaporization of the liquid refrigerant flowing between these heat exchangers.

In order to circulate air from Within the enclosure through the inner or evaporator compartment 6 for conditioning, or cooling, the air, there is provided an inner or evaporator fan 11 in the lower portion of the evaporator compartment upstream from the evaporator 8; The fan is driven by a shaft 12a extending from a multi-speed motor 12' mounted in the barrier 3. The motor '13 is of the type which may operate at a range of speeds depending upon the power supplied to the motor. Air

through the outlet opening 18. As illustrated in FIG.

1, both of the fans 11 and 16 .are powered by the same driving means, namely, the multi-speed motor 12 through the shaft 12a. This is a common arrangement for driving the separate fans of an air conditioner, however, separate motors could be used to drive each of the fans and the corresponding .air flow and results accomplished by these air streams would be the same.

When an air conditioning unit of this type is employed for cooling an enclosure, the heat exchanger 8 is operated as an evaporator and extracts heat from the air circulated through the evaporator compartment '6 from within the room. The heat exchanger 7 is operated as a condenser and discharges the heat taken up by the refrigerant flowing through the evaporator 8, to the outdoor air being circulated through the outer compartment 4. The outdoor air cools the condenser 7, thereby condensing the high pressure high temperature refrigerant flowing into it from the exhaust tubing 10.

Many air conditioning units of this general type now on the market provide a means for reducing the speed of the fans, or at least for reducing the speed of the evaporator fan, in order to permit the operator to reduce the noise of the unit whenever the cooling requirements within the room are such as to permit reduced capacity operation of the unit. 1 In the illustrated embodiment of the invention, .a fan speed control means 19 having a knob 19a accessible from the front of the unit is provided for changing the motor speed according to the desires of the operator. In FIG. 2, this fan speed control means is represented by the dotted line enclosure generally designated by the reference numeral 19. Included in this control means is a selector switch 21 which, in the illustrated embodiment of the invention, is movable by the knob 19a between a pair'of contacts 22 and 23 to connect either of a pair of fan circuits across the power supply lines designated L 'and'L The first circuit, which will be referred to as the high speed circuit, is energized when the selector switch 21'is connected across the contact 22. This circuit includes the line 24 which connects with the high speed tap on the fan motor. fan motor 12 is shown connected in the high speed fan circuit across the power lines L and L The second, or low speed circuit, is energized by moving the fan speed selector switch 21 across the contact 23. The low speed circuit includes the line 26 which conducts current to the fan motor 12 through a reactance 27 connected to another of the motor taps. The reactance 27', When'connected in series with the fan circuit reduces the fan motor speed and achieves a reduction in the noise output of the fans. Any type of reactance may be'used for this purpose, such as an inductive or capacitive reactance or any combination of these. In the illustrated embodiment of the invention, the inductive reactance 27 is shown external to the fan motor 13, however, it will be understood that this reactance may well be incorporated as a part of the fan motor, such as, in the form of an inductive winding in the stator of the motor itself. Use of inductive reactance for changing the motor speed accomplishes this result without too great a power loss or heat dissipation in the reactance itself and is, therefore, more desirable than connecting a resistance or some other such current limiting device in series with the fan motor in the low speed fan motor circuit.

As may be seen in FIG. 2, thehigh speed circuit and In FIG. 2, the

the low speed circuit are shown connected to separate taps of the fan motor 12. This is illustrated in this way to indicate that the motor 12 may be of the type including a plurality of different inductive windings connected to separate taps leading to different power circuits. It will be understood, however, that when a reactance, such as the reactance 27, is external to the fan motor, then the separate external fan motor circuits may connect to the same tap of the fan motor.

As was previously mentioned, the components of a refrigeration system are usually designed for specific operating conditions under which they perform at optimum efficiency. In a refrigeration system of this type, the evaporator and the condenser are most likely designed for optimum performance at that quantity of air fiow provided by the fans when operated at high speed. Whenever an air conditioning unit of this type includes a fan motor which may be operated at lower or reduced speeds, this usually creates conditions for which the components of the system are not designed. Thus, as mentioned previously, when the operator reduces the evaporator fan speed while the indoor heat load remains high, and the outdoor temperature then falls, the overall result is that the evaporator operates too cold and causes frost accumulation thereon. The frost greatly restricts the air flow through the inner compartment and greatly affects the ability of the unit to properly condition the room.

In order to prevent this condition and other conditions deleterious to operation of the unit from occurring when the evaporator fan speed is reduced, there is provided a throttling device or flow restricting means 28 in the suction line leading from the evaporator to the compressor. The throttling device is designed to restrict the flow of refrigerant from the evaporator to the compressor Whenever the fan motor is operated at low speed. As may be seen in FIG. 2, the throttling means 28 comprises a valve having a valve opening 30 therein across which a valve body 31 is moved by a solenoid 32 whenever throttling of the refrigerant from the evaporator to the compressor is required. Whenever the valve 31 is moved into its valve seat 31a across the opening 30, flow is restricted as compared to that which may flow through the restricted opening 29 in the valve body 28. The valve or restricting body 31 is energized simultaneously with the conditioning of the fan motor to operate at its low speed operation. This is accomplished, in the illustrated embodiment of the invention by connecting the solenoid 32 in series with the line 26 leading to the low speed contact 23 of the fan speed selector control means 19. The solenoid 32 is, therefore, disclosed in parallel across the power lines with the fan motor 12 when the motor is connected in its low speed circuit. Upon energization of the line 26 or the low speed fan circuit, current is carried through line 34 to the solenoid 32 moving the restricting valve 31 across the opening 30 of the throttling device to provide a predetermined restriction within the suction line 5 thereby reducing the effective rate of refrigerant flow through the system.

The effect of the throttling device in the suction line 5 is to prevent boiling off of liquid refrigerant in the evapo rator too rapidly thereby maintaining the temperature of the evaporator higher than would be the case if the refrigerant were allowed to circulate through the system in its normal manner. Whenever the fan speed selector switch 21 is disconnected from the contact 23, thereby interrupting the low speed fan circuit, the current flow through the line 34 leading to the solenoid valve 32 is also interrupted. The solenoid then permits the valve member 31 to return to its normal position, which is the position illustrated in FIG. 2 and valve opening 30 is then completely open and permits unrestricted refrigerant flow through the suction line 5.

While in accordance with the patent statutes there has been described what at present is considered to be the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention and it is, therefore, the aim of the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An air conditioning unit for conditioning the air within a room comprising a casing adapted for mounting in an outer wall of said room; said casing including openings communicating with indoor and outdoor air respec tively; a refrigeration system mounted in said casing including a compressor, a condenser, and an evaporator, a discharge tube and suction tube connecting said condenser and said evaporator respectively with said compressor in refrigerant flow relationship; an evaporator fan and a condenser tan in said casing for circulating air streams from said room and from the outdoors over said evaporator and said condenser; fan speed control means in said unit for selectively conditioning said evaporator fan to operate at reduced speed; and suction tube throttling means energized simultaneously by said fan speed control means when said evaporator fan is conditioned for reduced speed operation, said suction tube throttling means simultaneously restricting refrigerant flow through said suction tube from said evaporator to said compressor when said fan speed control means conditions said fan to operate at reduced speed so that refrigerant flow through said system and the capacity thereof are simultaneously decreased with the reduction in air flow over said evaporator.

2. An air conditioning unit for conditioning the air within a room comprising a casing adapted for mounting in an outer wall of said room; said casing including openings communicating With indoor and outdoor air respectively; a refrigeration system mounted in said casing and including a compressor, a condenser, and an evaporator, exhaust tubing and suction tubing respectively connecting said condenser and said evaporator with said compressor in refrigerant flow relationship; an evaporator fan and a condenser fan in said casing for circulating air streams from said room and from the outdoors respectively over said evaporator and said condenser; fan speed control means mounted in said unit for selectively connecting said evaporator fan into first and second electrical circuits; said first circuit adapted to operate said fan motor at a relatively high speed; said second circuit adapted to connect a reactance in series with said fan motor for reducing the operating speed thereof as compared to the speed of o eration of said fan motor in said first circuit; a throttling valve in said suction tube for restricting refrigerant flow through said suction tube between said evaporator and said compressor; means for simultaneously energizing said throttling valve when said fan speed control connects said fan motor into said low speed fan circuit so that refrigerant flow through said system and the capacity thereof are simultaneously decreased with the reduction in air fiow over said evaporator.

3. An air conditioning unit for conditioning the air Within a room comprising a casing adapted for mounting in an outer Wall of said room; said casing including openings communicating with indoor and outdoor air respectively; a refrigeration system in said casing including a compressor, a condenser and an evaporator, a discharge tube and a suction tube connecting said condenser and said evaporator respectively With said compressor in refrigerant flow relationship; an evaporator fan and a condenser fan in said casing for circulating air streams from said room and from the outdoors over said evaporator and said condenser; a single fan motor for operating said evaporator and condenser fans; fan speed control means accessible from the front of said casing for selectively connecting said fan motor into a high speed circuit or a low speed circuit; a throttling valve in said suction line between said compressor and the evaporator; said throttling valve including a solenoid operated valve member movable from an open position wherein said valve permits unrestricted refrigerant fiow through said suction tube to a second position wherein a predetermined restriction to refrigerant flow is provided in said suction tube; and means electrically connecting said solenoid in parallel with said low speed circuit of said fan motor for simultaneously energizing said solenoid operated valve member to restrict said suction tube when said fan speed control means connects said fan motor into said low speed fan circuit so that refrigerant flow through said system and the capacity thereof are simultaneously decreased with the reduction in air flow over said evaporator.

References Cited in the file of this patent UNITED STATES PATENTS 1,757,044 Hansen May 6, 1930 2,338,362 Smith Jan. 4, 1944 2,361,090 Dickey Oct. 24, 1944 2,970,455 Slattery L. Feb. 7, 1961 

